Low cost optical pump laser package

ABSTRACT

Laser diode packages include a rigid thermally conductive base member that includes a base member surface situated to support at least one laser diode assembly, at least one electrode standoff secured to the base member surface that has at least one electrical lead having a first end and a second end with the first end secured to a lead surface of the electrode standoff, and a lid member that includes a lid portion and a plurality of side portions extending from the lid portion and situated to be secured to the base member so as to define sides of the laser diode package, wherein at least one of the side portions includes a lead aperture situated to receive the second end of the secured electrical lead that is insertable through the lead aperture so that the lid member extends over the base member to enclose the laser diode package.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/372,963, filed Apr. 2, 2019, which is a continuation of U.S.application Ser. No. 15/849,057, filed Dec. 20, 2017, now U.S. Pat. No.10,283,939, issued on May 7, 2019, which claims the benefit of U.S.Provisional Patent Application No. 62/438,961, flied Dec. 23, 2016, allof which applications are incorporated by reference herein in theirentirety.

FIELD

The disclosure pertains to laser diode packages.

BACKGROUND

Laser diode packages are typically situated to generate substantialamounts of bright light in the form of laser radiation for variousapplications. Various optical, thermal, and mechanical characteristicsof packages can present design obstacles, resulting in conventionaldesigns having undesirable performance or features. Accordingly, a needremains for laser diode packages with fewer drawbacks.

SUMMARY

According to an aspect of the disclosed technology, apparatus include alaser diode package including a rigid thermally conductive base memberthat includes a base member surface situated to support at least onelaser diode assembly, at least one electrode standoff secured to thebase member surface that has at least one electrical lead having a firstend and a second end with the first end secured to a lead surface of theelectrode standoff, and a lid member that includes a lid portion and aplurality of side portions extending from the lid portion and situatedto be secured to the base member so as to define sides of the laserdiode package, wherein at least one of the side portions includes a leadaperture situated to receive the second end of the secured electricallead that is insertable through the lead aperture so that the lid memberextends over the base member to enclose the laser diode package. In someexamples, at least one of the insulating electrode standoffs and atleast one of the electrical leads correspond to a first electrodestandoff and first electrical lead pair and a spaced apart secondelectrode standoff and electrical lead pair, wherein at least one of theside portions includes a side portion that includes a first leadaperture corresponding to the first electrical lead and a second leadaperture corresponding to the second electrical lead. In furtherexamples, the laser diode package includes an electrically insulatinggrommet having a ring member defining an aperture situated to receivethe second end of the at least one electrical lead, wherein the grommetis secured to the at least one side portion and the at least oneelectrical lead at the lead aperture. The laser diode package canfurther include an optical output terminal secured to the base memberand that includes an optical fiber optically coupled to an interiorregion of the laser diode package so as to receive laser beams emittedfrom the at least one laser diode assembly. In some optical outputterminal examples, at least one side portion including the lead aperturefurther includes an output terminal aperture having a shape thatcorresponds to a shape of the optical fiber output terminal. Inadditional optical output terminal examples, the base member includes aplurality of sub-members secured to the base member with each sub-memberhaving a common footprint and defining at least a portion of the basemember surface, and with each sub-member situated to receive at leastone of the laser diode assemblies so as to provide a laser diode packageoutput power scalability based on the quantity of sub-members, whereinat least one electrode standoff is secured to a first sub-member, andthe other sub-members include at least one internal electrode standoffelectrically coupled within the laser diode package to the electricallead secured to the electrode standoff. In some examples, the pluralityof sub-members includes a second sub-member with each at least one laserdiode assembly of the respective first and second sub-members includinga plurality of laser diodes situated to emit beams and to form a beamstack propagating in a common direction and having a slow axis of eachbeam parallel and spaced apart from each other and having a fast axis ofeach beam aligned with each other, wherein the common direction of thebeams stacks are the same and the beam stacks are combined with awavelength multiplexer or a polarization multiplexer secured to thefirst sub-member. In particular optical output terminal embodiments, oneor more of the laser diode assemblies includes a plurality of laserdiodes situated on separate steps of a mounting block to emit respectivelaser beams in a first common direction with each laser beam having aslow axis and a fast axis arranged so that the slow axes are paralleland spaced apart and the fast axes are parallel and spaced apart,wherein the one or more of the laser diode assemblies further includes aplurality of fast axis collimators respectively optically coupled to oneof the laser beams to collimate the fast axis, a plurality of slow axiscollimators respectively optically coupled to one of the fast axiscollimated laser beams to collimate the slow axis, a plurality ofturning mirrors respectively optically coupled to one of the fast axisand slow axis collimated laser beams to reflect the beam into a secondcommon direction so that the slow axes are parallel and spaced apart andthe fast axes are aligned to form a laser diode assembly beam stack,wherein the optical output terminal includes one or more focusing opticssituated to optically couple the laser diode assembly beam stack intothe optical fiber. In such particular optical output terminal examples,the one or more laser diode assemblies includes a first laser diodeassembly and a second diode assembly with the first common direction ofthe second diode assembly being opposite to the first common directionof the first laser diode assembly. In some examples, the laser diodepackage further includes an optical output terminal situated to receivelaser beams emitted from the at least one laser diode assembly andprovide an output for free-space propagation of the laser beams outsideof the laser diode package. According to some embodiments, the sideportions of the lid member are flexibly secured to the base member atleast in part with an epoxy. In other embodiments, the side portions areflexibly secured to the base member at least in part with one or more ofan epoxy, a weld, solder, a press-fit, snap-fit, a braze, or a fastener.According to some flexibly secured examples, the side portions include afirst pair of opposite side portions having a first length and a secondpair of opposite side portions having a second length greater than thefirst length and extending perpendicularly to the first length so as tojoin the first pair at respective ends of the first and second lengths,wherein epoxy is situated between the base member and the second pairproximate a center portion of the second length and absent from the endsof the second length. In some embodiments, the lead aperture extends toan edge of the at least one side portion opposite the lid portion so asto define an open-ended lead aperture. Further examples include the lidmember having a thickness that is selected in relation to the basemember so as to reduce a warping of the base member associated withthermal cycling of the laser diode package. In some examples, the lidmember and the base member comprise dissimilar metals with dissimilarcoefficients of thermal expansion. According to some embodiments, thebase member is made of copper or a copper alloy and the lid member ismade of aluminum According to further embodiments, the lid member is adeep drawn metal blank with the drawn sides corresponding to theplurality of side portions. In some embodiments, the lid member is afolded, cast, machined, or 3D printed lid member. In some laser diodepackages, there is only one laser diode assembly with only onesingle-emitter laser diode.

According to another aspect of the disclosed technology, methods includesecuring at least one electrode standoff to a rigid thermally conductivebaseplate member of a laser diode package and securing a first end of atleast one electrical lead having the first end and a second to the atleast one electrode standoff so that the electrical lead extend outsidea footprint of the baseplate member with the second end situated outsidethe laser diode package, and enclosing the laser diode package with alid member that includes a plurality of side portions that extendcontinuously from the a lid portion so as to define laser diode packagesides and that includes at least one lead aperture in at least one ofthe side portions that corresponds to a cross-section of the at leastone electrical lead extending outside the laser diode package, whereinthe enclosing includes inserting the second end of the secured at leastone electrical lead through the at least one lead aperture. In someexamples, the electrode standoff and the electrical lead comprise afirst electrical standoff and first electrical lead pair and a spacedapart second electrical standoff an electrical lead pair, and the one ormore side portions includes a side portion that includes a first leadaperture corresponding to the first electrical lead and a second leadaperture corresponding to the second electrical lead. Some embodimentsfurther include positioning an insulating grommet around the at leastone electrical lead extending outside the laser diode package andsecuring the grommet to the at least one side portion and the at leastone electrical lead at the lead aperture. Additional embodiments furtherinclude securing the side portions of the lid member to the baseplatemember with epoxy. Some embodiments further include securing at leastone laser diode assembly to the baseplate member.

The foregoing and other Objects, features, and advantages of thedisclosed technology will become more apparent from the followingdetailed description, which proceeds with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show perspective views of a laser diode package embodiment.

FIGS. 2-3 show perspective views of another laser diode packageembodiment.

FIG. 4 shows a plan view of a modular laser diode package embodiment.

FIG. 5 is a flowchart of a representative method.

DETAILED DESCRIPTION

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”Further, the term “coupled” does not exclude the presence ofintermediate elements between the coupled items.

The systems, apparatus, and methods described herein should not beconstrued as limiting in any way. Instead, the present disclosure isdirected toward all novel and non-obvious features and aspects of thevarious disclosed embodiments, alone and in various combinations andsub-combinations with one another. The disclosed systems, methods, andapparatus are not limited to any specific aspect or feature orcombinations thereof, nor do the disclosed systems, methods, andapparatus require that any one or more specific advantages be present orproblems be solved. Any theories of operation are to facilitateexplanation, but the disclosed systems, methods, and apparatus are notlimited to such theories of operation.

Although the operations of sonic of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthbelow. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed systems, methods, and apparatus can be used in conjunctionwith other systems, methods, and apparatus. Additionally, thedescription sometimes uses terms like “produce” and “provide” todescribe the disclosed methods. These terms are high-level abstractionsof the actual operations that are performed. The actual operations thatcorrespond to these terms will vary depending on the particularimplementation and are readily discernible by one of ordinary skill inthe art.

In some examples, values, procedures, or apparatus' are referred to as“lowest,” “best,” “minimum,” or the like. It will be appreciated thatsuch descriptions are intended to indicate that a selection among manyused functional alternatives can be made, and such selections need nothe better, smaller, or otherwise preferable to other selections.

As used herein, laser beams comprise optical radiation at wavelengths ofbetween about 100 nm and 10 μm, and typically between about 500 nm and 2μm. Examples based on available laser diode sources and optical fibersgenerally are associated with wavelengths of between about 800 nm and1700 nm. In some examples, propagating optical radiation is referred toas one or more beams having diameters, asymmetric fast and slow axes,beam cross-sectional areas, and beam divergences that can depend on beamwavelength and the optical systems used for beam shaping. Forconvenience, optical radiation is referred to as light in some examples,and need not be at visible wavelengths.

Typical laser diodes have emission regions having non-circularcross-sections. An emission region of a laser diode can be associatedwith a slow axis that is directed along a longest dimension of theemission region and a fast axis that is directed along a shortestdimension of the emission region. Along the slow axis, an emitted beamtends to have a smaller angular divergence than the angular divergencealong the fast axis. In addition, the slow axis tends to be associatedwith beam propagation in more transverse modes than beam propagation inthe fast axis so that a beam parameter product (corresponding to aproduct of an angular divergence and a beam dimension) measured alongthe slow axis is larger than that measured along the fast axis. Beamdivergences and diameters along the slow axis, the fast axis, or bothcan be adjusted with one or more lenses, prisms, or mirrors to provideselected beam characteristics.

Representative embodiments are described with reference to opticalfibers, but other types of optical waveguides can be used having square,rectangular, polygonal, oval, elliptical or other cross-sections.Optical fibers are typically formed of silica (glass) that is doped (orundoped) so as to provide predetermined refractive indices or refractiveindex differences. In some, examples, fibers or other waveguides aremade of other materials such as fluorozirconates, fluoroaluminates,fluoride or phosphate glasses, chalcogenide glasses, or crystallinematerials such as sapphire, depending on wavelengths of interest.Refractive indices of silica and fluoride glasses are typically about1.5, but refractive indices of other materials such as chalcogenides canbe 3 or more. In still other examples, optical fibers can be formed inpart of plastics. In typical examples, a doped waveguide core such as afiber core provides optical gain in response to pumping, and core andcladdings are approximately concentric. In other examples, one or moreof the core and claddings are decentered, and in some examples, core andcladding orientation and/or displacement vary along a waveguide length.

As used herein, numerical aperture (NA) refers to a largest angle ofincidence with respect to a propagation axis defined by an opticalwaveguide for which propagating optical radiation is substantiallyconfined. In optical fibers, fiber cores and fiber claddings can haveassociated NAs, typically defined by refractive index differencesbetween a core and cladding layer, or adjacent cladding layers,respectively. While optical radiation propagating at such NAs isgenerally well confined, associated electromagnetic fields such asevanescent fields typically extend into an adjacent cladding layer. Insome examples, a core NA is associated with a core/inner claddingrefractive index, and a cladding NA is associated with an innercladding/outer cladding refractive index difference. For an opticalfiber having a core refractive index n_(core) and a cladding indexn_(clad), a fiber core NA is NA=√{square root over (n_(core) ²−n_(clad)²)}. For an optical fiber with an inner core and an outer core adjacentthe inner core, a core NA is NA =√{square root over (n_(inner)²−n_(outer) ²)}, wherein n_(inner) and n_(outer) are refractive indicesof the core and the outer core, respectively. Optical beams as discussedabove can also be referred to as having a beam NA which is associatedwith a beam angular radius. While multi-core step index fibers aredescribed below, gradient index designs can also be used.

In the examples disclosed herein, a waveguide core such as an opticalfiber core is doped with a rare earth element such as Nd, Yb, Ho, Er, orother active dopants or combinations thereof Such actively doped corescan provide optical gain in response to optical or other pumping. Asdisclosed below, waveguides having such active dopants can be used toform optical amplifiers, or, if provided with suitable optical feedbacksuch as reflective layers, mirrors, Bragg gratings, or other feedbackmechanisms, such waveguides can generate laser emissions. Optical pumpradiation can be arranged to co-propagate and/or counter-propagate inthe waveguide with respect to a propagation direction of an emittedlaser beam or an amplified beam.

The term brightness is used herein to refer to optical beam power perunit area per solid angle. In some examples, optical beam power isprovided with one or more laser diodes that produce beams whose solidangles are proportional to beam wavelength and inversely proportional tobeam area. Selection of beam area and beam solid angle can produce pumpbeams that couple selected pump beam powers into one or more core orcladding layers of double, triple, or other single or multi-clad opticalfibers. Beam cross-sectional areas, diameters, or other beam dimensionscan be described using boundaries that generally correspond to a zerointensity value, a 1/e value, a 1/e² value, a full-width half-maximum(FWHM) value, or other suitable metric.

Optical beams and optical elements are described in some examples withrespect to one or more axes. Typically, an axis includes one or morestraight line segments along which an optical beam propagates or alongwhich one or more optical elements are situated. Such axes can be bentor folded with reflective surfaces, so that axes need not be singlestraight line segments. Various lenses are described or may be used,including convex-convex, planoconvex, concave-concave, planoconcave,cylindrical, fresnel, zone plates, holographic, spherical, aspheric,combinations thereof. In convenient examples, cylindrical lenses havecylindrical surfaces that are arranged perpendicular to each other toprovide a cross-cylinder or crossed-cylinder lens or lens assembly. Intypical examples, planoconvex cylindrical lenses have a plano surfaceand a cylindrically convex surface that define focal axes that can beparallel to or collinear with an axial center of curvature associatedwith the cylindrically convex surface. Beams are typically incident tosuch lenses parallel to an optical axis that is perpendicular to theplano surface. Such beams tend to focus along an axis (e.g., slow axis,fast axis) perpendicular to the focal axes and optical axis, andcollimated beams tend to brought to a focus with respect to that axis atthe focal axis. It will be appreciated that focal axes can be other thanstraight, depending on the characteristics of the lens. In somecross-cylinder examples, a first and second objective are spaced apartalong an optical axis and provide a set of corresponding focal axeswhich are perpendicular to each other and intersect each other at afocal plane.

In various embodiments, optical components, such as lenses, mounts,housings, etc., are registered to other optical components. Surfaces oftwo or more optical components can be registered so as to align thecorresponding optical components or to align other optical components orbeams. Such registration and alignment can occur axially or transverselyor in other ways suitable to provide corresponding alignment of opticalcomponents and beams. The term “surface” is used in connection withregistering optical components, and it will be appreciated surfaces caninclude other features, including edges, planes, threads, serrations,textures, chamfers, notches, detents, clamping members, etc., and suchsurfaces can be arranged in orientations other than parallel orperpendicular to different features of optical components.

Laser diode package examples typically provide a housing to conduct heatout of the package (e.g., through a housing base), provide a protectiveenclosure from the external environment for the optics, lasers, andother components, and provide a mechanically stable platform for opticaland substructure attachment that will maintain internal opticalalignments throughout use, provide electrical feedthroughs of sufficientcurrent handling and optical feedthroughs of sufficient size, andprovide fastening locations for attaching (e.g., with screws or clamps)the housing to a rigid support that will thermally conduct heat awayfrom the base of the laser package housing. Packages with a rigid wallconsisting of Kovar or cold rolled steel, or copper walls, with a copperor copper/moly or copper/tungsten base, and copper or copper-cored leadswithin a ceramic or glass feedthrough, can provide the correspondingheat transfer. A separate lid is later attached via welding, solder, orepoxy, and the optical feedthrough port that is typically a part of theoptical train is attached to a wall of the package, and not to thebaseplate. Such configurations are susceptible to optic or fibermovement with the walls of the package, which are mechanically removedfrom the laser/optics typically attached to the base of the package.Additionally, during fabrication and brazing or firing of the electricalpins to the wall, the materials in the base, typically copper or alloyof copper, anneal during the firing process, causing the base to becomesoft and easily deformed. Holes used to screw down packages will oftenresult in a slightly deformed base surface, causing a non-flat base onthe package. Subsequent attachment of the package to other surfaces willresult in a gap between the package and the mounting surface, reducingthermal transfer, increasing operating temperature of laser diodeswithin the package, and reducing reliability or varying laser wavelengthoutside of acceptable tolerances for particular applications.

To mitigate the aforementioned problems, very thick baseplates can beused along with harder but less thermally conductive materials(aluminum, copper/moly, or copper tungsten), or very thin mounting tabsthat deform independent of the package, but provide little downwardpressure across the package, especially in larger packages (greater than1.cm sq). In typical examples, an entire interior surface of the laserdiode package and electrical pins is gold plated to providesolderability for various diode package components, but the gold platingcan be applied to some surfaces unnecessarily, such as side surfaces,thereby wasting gold material and increasing costs. As the packagehousings increase in size, the packages become prohibitively expensiveand heavy, which increases cost, decreases suitability for variouslow-weight applications, and increases susceptibility to stress andhandling damage. Multiple pins or large pins are needed for largercurrents, but the connectors typically needed are relatively expensive.

A base can be selected that is made of a material with acceptably highthermal conductivity (often Cu or CuW), and mated to side-wallsmanufactured out of a less thermally conductive, but more dimensionallystable material (such as an alloy like Kovar, or a less expensivestainless steel alloy), with the mating performed via a relatively hightemperature soldering or brazing process. The high temperature processsignificantly softens the material used in the baseplate. Additionally,the electrical connectors (usually Cu or Cu alloy conductor with a glassor ceramic insulator) are mounted through the wall of the packagethrough a high temperature process which can further soften thebaseplate material. A base can also be selected where the base and thewalls are made from the same material (usually having a. sufficientlyhigh thermal conductivity which is balanced with the needs fordimensional stability), and the center of the package is machined awayinto a “bathtub-like” configuration leaving a monolithic structure.Although this process foregoes the high temperature brazing process toattach the walls, the electrical connectors and insulators are insertedinto the side walls and secured with a high temperature brazing process,and therefore the package material is again softened. A large amount ofmachining with complex tolerances is required and a larger surface areawhich must be plated. A lid can be a stamped or machined flat “plate”which is attached via adhesive, mechanical clamping, welding orsoldering.

In representative example of the disclosed technology herein, a laserdiode package platform provides a rigid base that has a high thermalconductivity and high hardness throughout package fabrication andprocessing, resulting in a robust, lower cost laser diode package thatwould be otherwise achievable. A non-annealed copper (¼, half, ¾ or fullhard) or copper alloy baseplate with machined features for opticalmounting and flat base is plated for solderability (e.g., with gold).The package walls do not continuously extend from the base and are nototherwise attached nor is the lid, but instead a deep-drawn lid memberthat includes the package walls is installed after assembly of theinternal components of the laser diode package is complete or nearlycomplete. This approach significantly reduces laser diode package costand provides an open platform that addresses difficulties associatedwith manufacturing in a “box” design.

In some examples, instead of glass or ceramic feedthroughs attached tothe package walls, electrical leads are attached via soldering to thebase with a ceramic standoff or similar feature. In typical examples,the electrical leads are flat, but could be other shapes as well. Theelectrical leads provide an internal electrical surface for wirebondingor other contact to internal electrical traces, and separate stressesfrom the leads to the wires. The lid member is attached during the laststages of assembly, and brought over the electrical leads via openingsin one or more walls of the shell. A gap between the lid member and theprotruding electrical leads is filled with an insulator of ceramic,glass, high temperature plastic, or other non-electrically conductivematerial. In typical examples, the insulator provides light blockage andadditional mechanical integrity to the lead/post assembly duringcustomer handling. The lid member can then be screwed, epoxied,soldered, or welded to the baseplate.

In some examples, a thermal expansion and contraction of the lid andbase is controlled through epoxy flexibility and/or mechanical slippageso as to inhibit deformation of the base or lid, yet maintain packageand internal component integrity and alignment and to provide a. sealagainst light leakage. In typical examples of the disclosed technology,package walls and a package lid are integrated into one part, andfeedthroughs are mounted to the package independent of the lid andwalls. Baseplate hardness can be retained throughout attachment of theceramic post and electrical leads, which can be accomplished withsoldering processes at a temperature below 350° C.

Herein, annealing generally refers to thermal processing, typically inmetals, that increases grain size and softens the annealed material.Brazing generally refers to process involving a filler metal having aliquidus above 450° C. Soldering generally refers to processes involvingfiller metals with a liquidus at or below 450° C. Soldering usuallyresults in a lower strength attachment as compared to brazing. Lowtemperature soldering generally refers to soldering processes where thesolder is liquidus at temperatures at or below 200° C. High temperaturesoldering processes typically occur above 350° C.

In representative examples herein, the baseplate is fabricated(machined, molded, cast, or stamped) from a simple plate structure ofsufficiently thermally conductive material (such as Cu or a Cu alloy).Because the baseplate does not undergo high temperature processingduring package fabrication, the baseplate and package retain an originalintegrity, and experience substantially reduced surface warping (e.g.,less than or equal to 50 μm, 30 μm, 10 μm, or 5 μm across a baseplatefootprint), and therefore resulting in a more robust and reliablepackage product. Additionally, because the baseplate is simpler tomanufacture (shorter machining time, fewer critical dimensions, no hightemperature processes, and reduced surface area to plate), manufacturingcosts are substantially reduced. The electrical connectors and standoffsare attached to the baseplate via a (relatively) low temperature solderprocess, which can be similar to solder processes used to attach one ormore other components to the baseplate.

To form the walls of the package, a lid member can be inexpensivelystamped from an acceptable material (e.g., an aluminum alloy) to form anupside down bathtub like structure that is placed over the baseplate.The lid member can be attached in a manner where the differences indimensional stability between the lid member and the baseplate withoutresulting in the application of stresses by the lid member to thebaseplate that could compromise the function or reliability of the laserpackage. The lid member can be secured to the baseplate with an adhesiveso as to limit or reduce the amount of heat and/or stress applied to thebaseplate. In additional examples, other securing mechanisms can beused, such as fasteners (e.g., screws) or a low temperature solderingprocess. The cross-section of the electrically conductive pins can bevaried in accordance with current requirements of the diode package,allowing high power/current operation without sacrificing reliability.Also, by removing the package sidewalls that are typically situated sothat beams emitted by the laser diodes become blocked, the baseplateprovides a platform for independent modular units of laser diodeassemblies to be added so as to scale output power of the package. Forexample, by placing the modular units within close proximity to eachother, the output of each modular unit can he combined into a singleafocal or fiber coupled output by polarization, wavelength, orgeometrically multiplexing the laser beams from the multiple modularunits in the laser diode package.

In FIGS. 1A-1C, an example of a laser diode package 100 is shown thatincludes a base member 102 having a base member surface 103 on which aplurality of laser diode assemblies 104 a-104 d are secured torespective carrier plates 106 a-106 b. A pair of electrode standoffs108, 110 are also secured to the base member 102 and a pair ofcorresponding electrodes 112, 114 are secured to the respectivestandoffs 108, 110 at electrode first ends 116 a, 118 a, with electrodes112, 114 extending passed the footprint of the base member 102 so thatthe opposite electrode second ends 116 b, 118 b are situated outside ofthe laser diode package 100. The first ends 116 a, 118 a of theelectrodes 112, 114 are situated proximate a plurality of laser diodes120 a-120 d of the laser diode assemblies 104 a-104 d so that the laserdiodes 120 a-120 d can be electrically coupled to the electrodes 112,114 (e.g., through wire-bonding in a series relationship) to receiveelectrical current and to emit corresponding laser diode beams. Thesecond ends 116 b, 118 b are coupled to an electrical source (riotshown) to provide the current for the laser diodes 120 a-120 d. Inrepresentative examples, one or both of the standoffs 108, 110 areceramic and electrically insulating. In some examples, all or a portionof at least one of the standoffs 108, 110 can be conductive. In someembodiments, an insulating material can be used to electrically insulatebetween the base member 102 and the standoffs 108, 110, or between therespective standoffs 108, 110 and the respective electrodes 112, 114. Inparticular examples, one of the electrodes 112, 114 can be electricallyconductively coupled to the base member 102 through the respectivestandoff 108, 110.

The laser diode package 100 can be secured to other system components orhousings with fasteners. For example, in fiber laser systems, aplurality of the laser diode packages 100 can be used as pump lasermodules, and the pump laser modules can be secured to a fiber lasersystem housing.

The laser diode assemblies 104 a-104 d further include fast axiscollimators 122 a-122 d and slow axis collimators 124 a-124 d that aresituated to receive the laser diode beams emitted from the respectivelaser diodes 120 a-120 d and to collimate the beams along respectivefast divergence axes 126 and slow divergence axes 128. The collimatedbeams are received by respective turning mirrors 130 a-130 d and turnedso that the beams are stacked with the slow axes parallel to each otherand the fast axes aligned to form a beam stack that is directed tofocusing optics 132 that optically couple the beams into an endface 134of an optical fiber 136. In typical examples, an objective lens 135 issituated to direct and focus one or axes of the beams at the endface 134for coupling into the optical fiber 136. The endface 134 is situated inan optical output terminal 138 secured to the base member 102, e.g.,with fasteners. An exterior portion 144 of the optical output terminal138 is aligned with an edge of the base member 102. In typical examples,the laser diodes 120 a-120 d emit beams with maximum average opticalpowers in the range of 10 watts to 25 watts. The quantity of laser diodeassemblies, laser diodes per assembly, and acceptance characteristics ofthe optical fiber 136 vary so that the total power of the combined beamstack coupled into the optical fiber 136 is in the range of 50 watts to300 watts for different embodiments.

Laser beam wavelengths can vary based on diode materials, and aretypically in the range of 700 nm to 1000 nm, though other wavelengths,including infrared and ultraviolet are also possible. Representativepackage embodiments have wavelengths selected for fiber laser pumpingapplications. In some examples, wavelengths are selected, narrowed, orlocked with frequency selective elements, such as volume Bragg gratingsthat can be coupled to individual laser diodes or to groups of beams(e.g., beam stacks) and can be positioned in the beam path or paths inthe laser diode package 100 where convenient to provide frequencylocking performance, e.g., between slow axis collimators and turningmirrors, between fast axis collimators and slow axis collimators,between fast axis collimators and respective laser diodes, betweenturning mirrors and focusing optics, within focusing optics, etc. Inparticular examples, laser beam wavelengths center around 808 nm, 915nm, or 976 nm, at a selected operating power and diode junctiontemperature. In some examples, laser diode assemblies can include onesingle-emitter laser diode, and some packages can include a single laserdiode assembly (e.g., one assembly having a single laser diode, twolaser diodes, three laser diodes, etc.). Some embodiments providefree-space coupling of the beam, beams, or combined beam stacks orstacks to the optical output terminal 138 without coupling the laserlight into an optical fiber. In such examples, the focusing optics 132can be omitted or modified so as to provide collimated free-spacepropagation of the beams outside of the laser diode package 100, e.g.,to external beam shaping optics, targets, or other laser componentssituated to receive the beams.

Representative examples of the laser diode package 100 also include alid member 146 that can be a singular, deep-drawn part having a lidportion 148 that defines a top of the laser diode package 100. In someexamples, the lid portion has a plurality of side portions 150 a-150 dthat can continuously extend from the lid portion 148 so as to definesides of the laser diode package 100. In further examples, the lidportion 148 can be folded, cast, machines, 3D printed, or formed inother ways, The side portion 150 a, include openings 152, 154, 156, suchas apertures, holes, slots, etc. In some examples, a single opening canbe defined on a selected side portion and in other examples differentopening can be defined on different selected side portions. The positionof the openings 152, 154 in the side portion 150 a respectivelycorrespond to the electrical leads 112, 114 extending outside the laserdiode package 100 when the lid member 146 is situated over the basemember 102 to enclose the laser diode package 100. The position of theopening 156 corresponds to the exterior portion 144 of the opticaloutput terminal 138 so that the optical output terminal 138 is enclosedwith the lid member 146 situated over the base member 102. With theplurality of laser diode assemblies 104 a-104 d, electrode standoffs108, 110 with secured electrical leads 112, 114, and optical outputterminal 138 secured to the base member 102, the lid member 146 isinserted over the second ends 116 b, 118 b of the electrical leads 112,114 at the openings 152, 154 and brought in position over the footprintof the base member 102 to enclose the laser diode package 100, Infurther examples, the lid member 146 can be omitted the electrodestandoffs 108, 110 can be situated to support the electrical leads 112,114 without support by the lid member 146. In different examples, theelectrode standoffs 108, 110 include an increased cross-section ormaterial strength, or are secured to the base member 102 with a higherstrength solder, fastener, or other fastening mechanism, or theelectrical leads 112, 114 are smaller, or a combination. For example,certain application may not require enclosure of the laser diode package100 due to another enclosure or environment where laser lightrestriction is less important.

A pair of insulating grommets 158, 160 include respective grommetopenings 162, 164 shaped to correspond with a cross-section of theelectrical leads 112, 114. With the lid member 146 situated over thebase member 102, the grommets 158, 160 are inserted over the electricalleads 112, 114 through the grommet openings 162, 164 and positioned atthe openings 152, 154. The grommets 158, 160 include interior grommetportions 166, 168 that bridge at least a portion of a gap between therespective electrical leads 112, 114 and side portion 150 a across theopenings 152, 154. In some examples, outer surfaces 170, 172 of theinterior grommet portions 166, 168 contact the side portion 150 a. Infurther examples, an adhesive secures the outer surfaces 170, 172 to theside portion 150 a. The grommets 158, 160 insulate the electrical leads112, 114 conducting the current powering the laser diodes 120 a-120 dfrom the lid member 146, which can be made of various conductive ornon-conductive material types, including copper and aluminum Suitableinsulating materials include high temperature ceramics, resins, andpolymers. In some examples, the grommets 158, 160 are a fluid materialthat can be flowed around the electrical leads 112, 114 inserted throughthe openings 152, 154 and cured with the lid member 146 in position overbase member 102 forming a tight insulating seal. The size differencebetween the openings 152, 154 and the cross-section of the electricalleads 112, 114 allows the lid member 146 to be positioned at an angle asthe side portion 150 a slides in relation to the electrical leads 112,114 to enclose the base member 102 so as to provide clearance betweenthe laser diode assemblies 104 a-104 d and the side portion 150 c. Thelaser diode package 100 with the lid member 146 secured over the basemember 102 and with grommets 158, 160 secured in place over theelectrical leads 112, 114 is shown in FIG. 1C.

In typical examples, as the openings 152, 154 of the lid member 146translate along the electrical leads 112, 114, the opening 156 cantranslate along a fiber termination 174. The opening 156 can be openended so that the opening 156 extends to an edge of the side portion 150a allowing clearance for the optical fiber 136 and for the positioningof the lid member 146 over the base member 102 while the optical fiber136 is coupled to the optical output terminal 138. The opening 156 canform a close, snug, or interference fit with the exterior portion 144 ofthe optical output terminal 138. An epoxy or other adhesive can be usedto secure any gap between the exterior portion 144 and the side portion150 a at the opening 156. In representative examples, the lid member 146is secured to the base member 102 with an adhesive, such as a hightemperature epoxy, along at least a portion of the region of contactbetween edges of the side portions 150 a-150 d and the base membersurface 103. In some examples, the adhesive is selectively applied to amiddle region where the longer side portions 150 a, 150 c contact thebase member surface 103. As the laser diode package 100 undergoesoperational cycling, the selective application allows the base member102 to be partly structurally uncoupled from the lid member 146 so thatthe base member 102 can expand or contract partly independently from thelid member 146. In further examples, the lid member 146 can bealternatively or additionally secured to the base member 102 throughwelding, soldering, press-fitting, snap-fitting, brazing, screw-typefastening or other fasteners, or a combination.

In representative examples, the thickness of the lid member 146 issmaller than the thickness of the base member 102 or reduced as comparedto a conventional thickness difference between package side and basemembers. In some deep drawn lid member examples, the lid member 146typically has a common thickness in the millimeter range, such as 0.05mm, 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, etc. The thickness of the basemember 102 is typically measured from a bottom surface of the basemember 102 to the surface of contact with the lid member 146 enclosingthe laser diode package 100. Thicknesses also are typically in themillimeter range, such as 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, orthicker. In examples where the thickness of the base member 102 isincreased, the additional thickness enhances the rigidity and flexuralstrength of the base member 102 and corresponding resistance todeflection during construction of the laser diode package 100 anddownstream implementation of the laser diode package 100 in largersystems or end-user applications. In general, the thickness differencealso allows various other package variations, performance improvements,and cost reductions to be realized. For example, with the lid member 102incorporating the package sides, typically with the lid portion 148 andside portions 150 a-150 d having a common thickness, a gold-plating canbe applied to the base member 102 for component solderability withoutwasting application of the same material to the sides of the package.

As discussed above, in different embodiments, the lid member 146 can bemade from aluminum, copper, or other materials. In some examples, thematerial of lid member 146 is different from the material of the basemember 102. For example, the base member 102 can be made of copper andthe lid member 146 can be made of aluminum. In some examples, the basemember 102 and the lid member 146 can be different materials that havematched or non-matched coefficients of thermal expansion (CTE),including with metals, ceramics, or composites. CTE can be selected fromavailable materials, including dissimilar materials, so as to reduce orminimize stress associated with a CTE mismatch. In some examples, thereduced thickness of the lid member 146 relative to the base member 102allows the side portions 150 a-150 d to strain during fabrication,installation, or operation and reduce a deflection of the base member102 associated with the strain. As shown, in representative embodimentsof the laser diode package 100, the electrical leads 112, 114 aresecured to electrode standoffs 108, 110. This provides an advantageousalternative to brazing electrode pins to the sides of laser diodepackages, as the firing of the pins to the sides anneals or softens thesides and attached or continuously formed baseplate resulting inbaseplate warping. In some examples, the material and/or thickness ofthe lid member 146 is selected so as to reduce a warping effect on thebase member 102 associated with being secured to the base member 102.Additionally, by using the lid member 146, even with an increase inthickness of the base member 102, the overall weight of the laser diodepackage 100 is reduced as compared to a housing that incorporates thesides into the baseplate. Such overall weight reduction and improvedthermal performance can be advantageous in devices used in aerospaceapplications where size, weight, and power (SWaP) concerns can beparamount. Also, weight and thermal improvements can allow package sizeincreases, allowing for additional laser diode emitters, for example, orincreased rigidity and/or strength improvements.

FIGS. 2-3 illustrate another example of a laser diode package 300 thatincludes a base member 302 and a pair of laser diode assemblies 304 a,304 b each situated to emit a set of laser beams propagating alongparallel propagation axes but in an opposite direction from the other. Apair of beam stacks are formed and received by a polarizationmultiplexer 306 that combines the beam stacks. Focusing optics 308receive the combined beam stacks and couple the light into an opticalfiber 310 coupled to an optical output terminal 312. A pair ofelectrical leads 314, 316 are secured to respective standoffs 318, 320that are secured to the base member 302. An internal electrical bus bar321 is secured to the base member 302 and provides an electrical pathfor completing a series circuit between the electrical lead 314 and thelaser diode assembly 304 a, and the laser diode assembly 304 b andelectrical 316.

A lid member 322 includes a lid portion 324 defining a top of the laserdiode package 300 and a plurality of side portions 326 a-326 d definingsides of the laser diode package 300. The side portion 326 a includes apair of openings 328, 330 that are situated to receive the electricalleads 314, 316 so that the lid member 322 can be positioned over thebase member 302 with the electrical leads 314, 316 secured to thestandoffs 318, 320 and base member 302. The side portion 326 d includesan opening 332 that extends to an edge of the side portion 326 d so thatas the lid member 302 is slidably engaging the electrical leads 314,316, the lid member 302 can be lowered at the side portion 326 c overthe optical output terminal 312. The lid member 322 and base member 302are secured together along at least a portion of a contact surface 333so as to enclose the laser diode package 300. With the lid member 322 inposition and contacting the base member 302, a pair of insulatinggrommets 334, 336 are inserted over the protruding electrical leads 314,316 so as to surround the electrical leads 314, 316 in the openings 328,330. The grommet 334, 336 are secured to the electrical leads 314, 316and the side portion 326 a.

In FIG. 4, an example of a modular laser diode package 400 is shown thathas a base member 402 that includes three sub-members 404, 406, 408 thatcan have several substantially similar features that streamlinemanufacturability of different product categories and scalability todifferent package output powers or other characteristics, such asnumerical aperture. A pair of electrodes 410, 412 extend outside thelaser diode package 400 from standoffs 414, 416 secured to thesub-member 404. Each of the three sub-members 404, 406, 408 includesrespective laser diode assemblies 418, 420, 422 situated to emitrespective sets of laser diode beams are directed into beam stacks 419,421, 423. The beam stacks 419, 421, 423 are directed with turningmirrors 424, 426, 428 towards a focusing objective 430 situated in anoptical output terminal 432 to become focused and coupled into anoptical fiber 434. The beam stacks 419, 421, 423 can be combined invarious ways. For example, one or more of the beam stacks 419, 421, 423can be geometrically multiplexed so as to lie one above the other (i.e.,in or out of the plane of FIG. 4) or side by side. One or more of thebeam stacks 419, 421, 423 can be polarization multiplexed with theturning mirrors 424, 426. In representative examples, one or more of thebeam stacks 419, 421, 423 are emitted at different wavelengths, and theturning mirrors 424, 426 include dichroic coatings so pass or reflectthe corresponding incident beam stacks 419, 421, 423. In some examples,the sub-member 406 includes standoffs 436, 438 and the sub-member 408includes standoffs 440, 442 that can be used to connect one or moreinternal conductive members to complete one or more circuits with theelectrical leads 410, 412 and provide a current to the laser diodeassemblies 418, 420, 422. In sonic examples, the electrical leads 410,412 can be secured to other locations of the base member 402. Forexample, a pair or multiple pairs of electrodes can be coupled in fromthe left side of sub-members 404, 406, 408 in FIG. 4. The sub-members404, 406, 408 are generally flat and without side members that wouldobstruct beam stack propagation so that laser diode packages of varioussizes and configurations can be made and the footprint of the basemember 402 can be modularly varied.

FIG. 5 shows an example of a method 500 of forming a laser diodepackage. At 502, at least one electrode standoff is secured to a rigidthermally conductive baseplate member of a laser diode package and afirst end of at least one electrical lead is secured to the at least oneelectrode standoff so that the electrical lead extends outside afootprint of the baseplate member with the second end situated outsidethe laser diode package. At 504, the laser diode package is enclosedwith a lid member that includes a plurality of side portions that extendfrom a lid portion so as to define laser diode package sides and thatincludes at least one lead aperture in at least one of the side portionsthat is situated to receive the at least one electrical lead extendingoutside the laser diode package. The enclosing typically includesinserting the second end of the secured at least one electrical leadthrough the at least one lead aperture. In representative examples, at506, at least one laser diode assembly can be secured to the baseplatemember. At 508, an insulating grommet can be positioned around the atleast one electrical lead extending outside the laser diode package andthe grommet can be secured to the at least one side portion and the atleast one electrical lead at the lead aperture. In some examples, at510, the side portions of the lid member can be secured to the baseplatemember with epoxy, fasteners, or other securing mechanism.

In view of the many possible embodiments to which the principles of thedisclosed technology may be applied, it should be recognized that theillustrated embodiments are only representative examples and should notbe taken as limiting the scope of the disclosure. Alternativesspecifically addressed in these sections are merely exemplary and do notconstitute all possible alternatives to the embodiments describedherein. For instance, various components of systems described herein maybe combined in function and use. We therefore claim all that comeswithin the scope and spirit of the appended claims.

We claim:
 1. A laser diode package, comprising: a first base member and at least one additional base member, each base member comprising at least one laser diode assembly including a plurality of laser diodes; at least one first electrode standoff secured to the first base member, the at least one first electrode standoff having at least one external electrical lead extending from an interior region of the laser diode package to a position outside the laser diode package; an optical output terminal secured to the first base member, the optical output terminal including an optical fiber optically coupled to the interior region of the laser diode package to receive laser beams emitted from the at least one laser diode assembly of the first base member; at least one additional electrode standoff coupled to the at least one additional base member, the at least one additional electrode standoff configured to support an internal electrical lead electrically coupled within the interior region of the laser diode package to the at least one external electrical lead coupled to the at least one first electrode standoff; and wherein the at least one additional base member is positioned relative to the first base member such that the laser beams emitted from the at least one laser diode assembly of the at least one additional base member travel over the first base member and are received by the optical output terminal.
 2. The laser diode package of claim 1, wherein: the at least one additional base member is a second base member comprising a second electrode standoff configured to support a second electrical lead; the laser diode package further comprises a third base member comprising a third electrode standoff configured to support a third electrical lead; the second and third electrode leads are electrically coupled to the external electrical lead within the interior region of the laser diode package; and wherein the second and third base members are positioned relative to the first base member such that the laser beams emitted from the at least one laser diode assembly of the second and third base members travel over the first base member and are received by the optical output terminal.
 3. The laser diode package of claim 1, wherein: each laser diode assembly is configured to emit a respective set of laser diode beams directed into a respective beam stack; and wherein the first base member and each additional base member each comprise respective optics configured to direct the respective beam stacks into the optical output terminal of the first base member.
 4. The laser diode package of claim 3, wherein the respective beam stacks are emitted at differing wavelengths, and wherein the optics comprise dichroic coatings configured to selectively transmit or reflect the corresponding beam stacks.
 5. The laser diode package of claim 3, wherein the respective beam stacks are geometrically multiplexed.
 6. The laser diode package of claim 3, wherein the respective beam stacks are polarization multiplexed.
 7. The laser diode package of claim 1, wherein each base member is flat without side members.
 8. The laser diode package of claim 1, further comprising a lid member having a top portion and side portions extending from the top portion, the lid member sized to extend over the first base member and at least one additional base member such that the first base member and at least one additional base member are contained within the lid member and such that the side portions are secured to an outer perimeter of the first base member and at least one additional base member to define sides of the laser diode package.
 9. The laser diode package of claim 8, wherein at least one of the side portions includes an electrode opening configured to insertably receive the at least one external electrical lead of the first base member before the lid extends over the base member and at least one additional base member to enclose the laser diode package.
 10. A laser diode package, comprising: a base member; a first sub-member disposed on the base member, the first sub-member comprising a laser diode assembly including a plurality of laser diodes, at least one electrode standoff, an optical output terminal including an optical fiber optically coupled to an interior region of the laser diode package, and at least one electrical lead coupled to the at least one electrode standoff and extending past an outer perimeter of the base member; second and third sub-members disposed on the base member, the second and third sub-members each comprising a laser diode assembly including a plurality of laser diodes, at least one electrode standoff, and one or more internal conductive members coupling the at least one electrode standoff to the at least one electrical lead of the first sub-member; and a lid member having a top portion and side portions extending from the top portion, the lid member sized to extend over the base member such that sub-members are contained within the lid member and such that the side portions are secured to the base member to define sides of the laser diode package, wherein the side portions of the lid are partially secured to the base member such that the base can expand and contract independently of the lid.
 11. The laser diode package of claim 10, wherein: each laser diode assembly is configured to emit a respective set of laser diode beams directed into a respective beam stack; and wherein each sub-member comprises respective optics configured to direct the respective beam stacks into the optical output terminal.
 12. The laser diode package of claim 11, wherein the respective beam stacks are emitted at differing wavelengths, and wherein the optics of at least the first and second sub-members comprise dichroic coatings configured to selectively transmit or reflect the corresponding beam stacks.
 13. The laser diode package of claim 11, wherein the respective beam stacks are geometrically multiplexed.
 14. The laser diode package of claim 11, wherein the respective beam stacks are polarization multiplexed.
 15. The laser diode package of claim 10, wherein each sub-member is flat without side members.
 16. The laser diode package of claim 10, wherein at least one of the side portions includes an electrode opening configured to insertably receive the at least one electrical lead of the first sub-member before the lid extends over the base member to enclose the laser diode package.
 17. The laser diode package of claim 16, further comprising an insulating grommet disposed over the at least one electrical lead of the first sub-member and disposed within the electrode opening.
 18. The laser diode package of claim 10, further comprising a fourth sub-member disposed on the base member, the fourth sub-member comprising a laser diode assembly including a plurality of laser diodes, at least one electrode standoff, and one or more internal conductive members coupling the at least one electrode standoff to the at least one electrical lead of the first sub-member. 